You cannot build phonegap locally on win 7.
Configure your phonegap.local.properties to do a remote phonegap build.
You will have to sign up for an account first.

Code:

If using PhoneGap, configure the phonegap.local.properties file to indicate which platforms you're building for. This file contains information you need to pass to the Adobe PhoneGap Build site to create your app - PhoneGap only lets you specify one platform at a time:
phonegap.platform=ios
phonegap.build.remote=true
phonegap.build.remote.username=<Your_PhoneGap_Username>
phonegap.build.remote.password=<Your_PhoneGap_Password>